In the field of prefilled ready-to-use syringes, devices have already been described that make it possible to determine whether or not the syringe has already been used. These devices generally relate to the distal end of the syringe, that is to say to the needle end of the syringe. Thus it has been proposed for the needle to be covered with a cap that has to be broken before the syringe can be used.
However, in the case of prefilled syringes, it is useful to provide a device preventing access to the piston. It is also useful to provide a device preventing the piston from being withdrawn. This is because it can happen that the actuating rod that actuates the piston is removed and the piston is then punctured with a needle to inject into the syringe a liquid or component that is unforeseen or unauthorized. The rod is then refitted to the piston.
During the process of manufacture of this type of syringe, the syringes are filled in a sterile environment then packaged and possibly sterilized. It is between these two steps of filling and packaging that the internal chamber of these syringes must not be exposed or that the drug it contains must not be contaminated.
Document EP 0 738 517 describes an open clip that is slipped, while the piston actuating rod is already mounted, over the flange situated on the proximal part of the body of the syringe so as to prevent movement and/or withdrawal of the syringe piston. However, this clip, because it is open, can easily be removed and then reinstated on the flange of the syringe. It cannot therefore be used to deny access to the piston. Nor does it prevent withdrawal of the piston.
Other systems said to be “closed” exist, but the withdrawal of the piston is prevented only when the piston actuating rod is present.